Asbestos has a needle-like crystal structure obtained by serpentine or hornblende transforming into a fibrous form. Examples of such types of asbestos include chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite. These types of asbestos exhibit excellent heat resistance and durability and are inexpensive, and were therefore widely used in a variety of technical fields in the past. Specifically, asbestos-containing substances that contain such types of asbestos were used in fillers for slate sheets, water pipes, fireproof covering materials, brake pads, gaskets, heat insulating boards, ropes, packings, acetylene cylinders, and the like.
However, because it has been established that these types of asbestos can be a primary cause of health problems such as pulmonary asbestosis, lung cancer and malignant mesothelioma, new uses have been banned in recent years. In addition, because continued use of asbestos-containing members used in the past involves risks, there is a need to rapidly detoxify asbestos using methods that do not have an adverse effect on humans and the environment.
Methods for treating such types of asbestos include melting by heating to 1500° C. or higher, chemical decomposition by reacting with prescribed asbestos treatment agents, and burial in landfill sites.
One example of such a detoxification method involving chemical decomposition is the method disclosed in Patent Document 1. In the method disclosed in this document, an asbestos-containing waste material is brought into contact with an aqueous solution of a detoxification (an asbestos treatment agent) to which is added a fluoride (a fluoride salt or hydrofluoric acid of an alkali metal, alkaline earth metal or ammonia) and a mineral acid (hydrochloric acid, sulfuric acid, nitric acid, or the like), and applying ultrasonic vibrations while allowing the solution to stand (or while stirring the solution).
In addition, Non-Patent Document 1 discloses another example of a method for detoxifying asbestos using an asbestos treatment agent that contains a mineral acid and a fluoride.